For example, with an increase in miniaturization of the circuit structures of semiconductor devices, substrate processing apparatuses used for manufacturing processes of semiconductor devices have been required even more to set their process chambers for accommodating semiconductor substrates to have very high cleanliness.
Under the circumstances, for example, Patent Document 1 discloses a technique in which a silicon crystal body is placed inside a process chamber at a region to face plasma. Contaminants are deposited on the surface of the silicon crystal body and can be easily removed by acid solution cleaning, thereby increasing the cleanliness of an area to be exposed to plasma within the process chamber.
Further, Patent Document 2 discloses a technique in which a cleaning gas comprising a nitrogen-containing compound and a fluorine-containing compound is supplied into the process chamber of a deposition apparatus and plasma is generated. Consequently, residual substances present within the process chamber are changed into volatile products and thereby removed.
Furthermore, Patent Document 3 discloses a technique in which a gas is supplied into a process chamber and turned into plasma. This plasma is used for performing sputter etching to remove contaminants from a ceramic member disposed inside the process chamber.
However, according to the conventional techniques described above, it has become difficult to meet cleanliness required in recent years, because of the following reasons. Specifically, the interior of a process chamber suffers corrosion of metal members due to corrosive gas, such as a fluorine-containing compound. Alternatively, the interior of a process chamber suffers damage of members disposed therein due to sputtering or re-deposition of sputtered contaminants.
For example, a step of forming gate oxide films in semiconductor devices is important, because this step has a decisive influence on the characteristic of transistors. Since metal contaminants, such as iron (Fe) and copper (Cu), greatly and adversely affect the characteristic of transistors, it is required to provide a decontamination technique that can attain higher cleanliness than the conventional technique.
On the other hand, as another process chamber cleaning method, the process chamber may be opened to the atmosphere and subjected to a wiping treatment with purified water or solvent. However, where a high level of cleanliness is required, as described above, the cleanliness may rather be lowered and unsatisfactory due to contaminants carried into the process chamber opened to the atmosphere. Further, in order to set the process chamber opened to the atmosphere, it is necessary to perform operations of disassembling and reassembling the process chamber, which are troublesome and take a long time. This brings about a technical problem such that the operation ratio of the substrate processing apparatus is significantly decreased.    [Patent Document 1] Jpn. Pat. Appln. KOKAI Publication No. 2002-353206    [Patent Document 2] Jpn. Pat. Appln. KOKAI Publication No. 9-232299    [Patent Document 3] Jpn. Pat. Appln. KOKAI Publication No. 11-3878